ON THE SHEEP OF ZETLAND. l6$ 



But if not protected, it suffers greatly by falling 

 into mossy pits, and over rocks, and from the at- 

 tacks of birds of prey. 



Mr Stevenson, the Reverend Mr Singers, and 

 Mr Hog *, have each assigned causes for this af- 

 fection, which, as applied to the production of 

 blindness in Zetland, appear to me to be unsatis- 

 factory. 



Mr Stevenson ascribes it to the reflection of 

 heat and light, in very sunny and dry weather, 

 as it is observed, he says, to be more frequent 

 when the hills become scorched, and on hard 

 rocky soils, than on dark-coloured hills, covered 

 with heath. The parish of Belting, into which 

 the disease was first introduced, consists almost 

 entirely of dark-coloured mossy hills ; and this to- 

 pographical fact, coupled with the general damp- 

 ness of the climate of Zetland, tend to shew, that 

 the exciting causes mentioned by Mr Stevenson, 

 never had operated where the disease raged with 

 its greatest malignity. 



The Reverend Mr Singers conceives, that this 

 affection may be produced sometimes by the pol- 

 len of flowers, irritat ing the eyes of the sheep, when 

 blown in considerable quantity. In the hilly 



* A Treatise on the diseases of sheep, drawn up from 

 original communications presented to the Highland So- 

 ciety of Scotland, by Andrew Duncan junior, M. D. 

 transactions of ths Highland Society vol. iii. 



